Magnetic balance



Aug. 6, 1935. ROUX 2,010,245

MAGNET IC BALANCE Filed April 20, 1931 2 Sheets-Sheet 1 Aug. 6, 1935.oux 2,010,245

' MAGNETIC BALANCE Filed April 20, 1931 2 Shem-shag 2 22 34 20 30 76' JP76 J4 Patented Aug. 6, 1935 UNITED STATES PATENT" OFFICE MAGNETICBALANCE Germany Application April 20, 1931, Serial No. 531,487 InGermany May 2, 1930 12 Claims. (Cl. 33222) This invention relates tomagnetic balances for making vertical and horizontal intensitymeasurements of the earths field.

The invention and its aims and objects will be 6 best understood fromthe following description taken in connection with the accompanyingdrawings of one embodiment of the invention herein described and shownfor illustrative purposes, the true scope of the invention being moreparticularly pointed out in the appended claims.

In the drawings:

Fig. l is a cross section through apparatus of the class describedembodying one illustrative form of the invention;

Fig. 2 is a side elevation of a balance system embodying oneillustrative-form of the invention;

Fig. 3 is a top plan view of the balance system illustrated in Fig. 2;

Fig. 4 is a perspective view of a balance system embodying certainfeatures of the invention, one of the magnetic blades being omitted forthe sake of cleamess;

Fig. 5 is a top plan view of the parts represented in Fig. 4.

As shown in Fig. l the housing for the apparatus may convenientlyconsist of a generally cylindrical jacket composed of two parts 2 and 4closed at its front and rear ends by sutiable end plates not shown. Theparts 2 and 4 are connected on one side by hinges 6 and can be locked onthe other side by a catch 8 so that by releasing the latter and foldingback the top part 4, the space between the two end plates is exposed.The lower part 2 of the cylindrical casing may be provided with feet ii)if desired, while the upper part 4 carries a telescope and appurtenantparts which it is unnecessary to describe further herein. The whole casemay be surrounded by an insulating jacket if of cork or other insulatingmaterial covered on the outside by metal plates. The magnetic balancesystem is provided with the usual knife edge I6 resting upon suitableseats .of agate or other material of the required hardness, said seatsbeing carried on the inside faces of said end plates.

The above described housing is that described and claimed in myco-pending application Serial No. 398,667, filed October 10, 1929, nowPatent 1,976,636, of October 9, 1934 and is herein given as a convenienthousing to be used, but it is to be understood that the presentinvention is not to be considered as limited to any particular form ofhousing, as any suitable form of housing may be used within the scope ofthe invention. If desired reference may be made to said co-pendingapplication for a more detailed description.

Formerly balance systems were made in a single-piece but this provedobjectionable because it was found that changes in temperature exercisedan injurious influence which produced variations in the' magnetic forceof the magnetic blades and consequently avariation in the position ofequilibrium of the balance system, with the result that those variationsin the position of equilibrium produced by changes in the intensity ofthe earth's field and which it was desired to observe, could bedistinguished only with difliculty from the above referred to effectsproduced by variations in temperature. It has I therefore been proposedto make the balance or central .body portion of the balance system of adifferent material from that of which the magnetic blades were made,aluminum being generally used for said central body. The steel magneticblades were then secured to said central body by screws, and it wasendeavored so to position and arrange said screws that the shifting ofthe center of gravity due to variations in temperature would compensatethe effects of changes in magnetization due tovariations in temperature.It has been found nevertheless that even with this arrangement wheresaid parts of the balance system are composed of different materials, ifthese materials possess different coefficients of expansion, greatervariations in temperature give rise to desultory, uncheckable variationsin the position of equilibrium, because the magnetic'blades screwed tothe central body adhere with a certain amount of force to said centralbody and said blades therefore generally yield only when the differencebetween the expansion of the aluminum central body and that of saidsteel ma netic blades has attained a more or less considerable degree.Where the temperature variations are considerable, temperature errorsproduced by these uncheckable slippages may render measurements madewith magnetic balances absolutely valueless.

One of the objects of the present invention is to overcome theseobjections.

In accordance with the invention the central body l8 is made ofdifferent material from that of which the blades 20 are made, butpossessing .the same or practically the same coeillcient of possesssubstantially the same coefflcient of ex pansion. As under theseconditions the said balance or central body l8 and said magnetic bladesexpand to the same extent, injurious slippages cannot occur in spite ofthe fact that the said magnetic blades and central body are screwedtogether.

The present invention also contemplates the provision of means toeliminate or neutralize the effect of temperature. Any suitable meansmay be provided for this purpose, and in the illustrative embodiment ofthe invention, said means will preferably comprise compensating orbalance rods 22, 24 extending from opposite sides of the knife edge i6forming the fulcrum of the magnetic balance, said rods extendinglongitudinally of said magnetic blades 20, each of said rods beingprovided with a weight 26, 28 adjustable longitudinally thereof. Saidrods are composed of material having difi'erent coemcients of expansion,the construction and arrangement being such that changes in themagnetization of the magnetic blades due to variations in. temperaturewill be compensated by the simultaneously occuring shifting of thecenter of gravity of the entire balance system. The preliminaryadjustment in balanced position may be efiected as usual by looseningthe blade securing screws 30 and longitudinally adjusting the saidblades relative to said central body it for which purpose the holes 32through which said screws pass in said blades are extended somewhatlongitudinally of said blades. Fine adjustment can be secured byshifting the weight on one of said balance rods longitudinally of thelatter.

Referring to the drawings in the illustrative embodiment of theinvention, the magnetic blades 20, it are secured by screws 36 to thecentral body it which, in the illustrative embodiment of the inventionconsist of iron, said screws 3t) extending through longitudinallyextended slots 32 in said blades and engaging screw threaded holes insaid central body. In accordance with the invention said central bodywill preferably be hollow, so as to save weight. To this end it may, forexample, be made of a solid piece subsequently bored, or it may consistof a section of a quadrangular drawn tube or a piece of sheet metal bentto quadrangular shape and suitably welded. The fulcrum of the magneticbalance is formed by the usual knife edge it which projects beyond themagnetic plates at opposite sides or" the device and rests, as alreadystated, at its opposite end portions upon fixed seats of agate or othersuitably hard material. The compensating or balance rods 22 and 2textend from opposite sides of the knife-edge i8 and are carried by thecentral body. The weights lit, 28 are slidable longitudinally of saidrods and may be clamped in adjusted position thereon by clamping screwsso, be. Each of the two rods 22 and 26 has a difierent coeihcient ofexpansion, the rod 22 for example being of zinc, while the rod it is ofinvar, in the illustrative embodiment ofthe invention. The fineadjustment of the zero position for the measurement of vertical intensities, that is to say, for example, that of the horizontal meanposition of the magnetic axis, may then be eflecte'd by sifting oradjusting the weight it longitudinally of the invar rod 23, the weight26 having previously been adjusted in such a position upon the zinc rod22 that variations in the magnetization of the magnetic blades due tochanges in temperature, and variations in the position of equilibriumproduced thereby, are compensated by the shifting of the center ofgravity of the entire balance system relative to the knife edge It,produced by the variations in the length of the zinc rod 22. As themagnetic blades are positioned substantially symmetrically relative tothe knife edge l6, noticeable shifting of the center of gravity, due tovariations in their length in response to changes in temperature, willnot occur. It is therefore possible to efiect the compensation fortemperature practically independently from adjustment of the position ofequilibrium. Heretofore, on the other hand, it has practically alwaysbeen necessary to make a supplementary correction of the adjustment tocompensate for temperature changes for the particular locality in whichthe apparatus was to be used, particularly when the intensity of theearth field at the place where the observations are to be made variedmaterially from the intensity'of the earth field at the locality wherethe apparatus was made. Owing to the fact that the central body itcarrying the magnetic blades has the same, or substantially the samecoefiicient of expansion as that of said magnetic blades themselves, theexpansion and contraction of said central body and said magnetic bladeswill be uniform, so that the injurious slipp e cannot occur.

Referring to Figs. 4 and 5, the lateral walls of the central body whichdo not carry the magnetic blades are shown as broken away, in fact asentirely missing, so that the central body it is entirely open upon saidsides, and the compensatory rods 22, 2d are secured to the bottom wall35 of said central body by brackets 34, 3G for example (only one ofwhich is shown in Fig. 4) preferably within said body. Preferably alsothe bottom and top walls 36 and til will be more or less broken away. Bythese provisions the mass of said central body is materially reduced, sothat the heat content of said central body is reduced to the lowestpossible degree. This construction has the advantage that thetemperature between the central body and said magnetic blades isequalized much more rapidly, The ambient air thus contacts both with theinner and the outer surfaces of said central body so that throughout theentire magnet balance system a noticeable drop in temperature can hardlyoccur. Sources of error due to changes in temperature, and whichheretofore have made measurements with magnetic balances quite difllcultas usually carried out, have thus been eliminated to a very greatdegree.

Upon the upper side of the balance body it there is provided the usualmirror 38.

While herein the invention has been shown in its application to amagnetic balance for measuring vertical intensities, it will be apparentto those skilled in the art that the invention is equally applicable tomagnetic balances for measuring horizontal intensities. It will also beapparent that the central or balance body need not be of quadrangularshape as shown in the illustrative embodiment oi the invention, but thatany other suitable shape can be used.

I am aware that the invention may be embodied in other specific formsthan that herein illustrated without departing from the spirit oressential attributes thereof, and I therefore desire the presentembodiment to be considered in all respects as illustrative and notrestrictive,

til

reference being had to the appended claims 75 rather than to theforegoing description to indicate the scope of the invention.

I claim:

1. A balance system for magnetic balances comprising, in combination, anoscillatory balance body and magnetic blades carried by said body, saidbalance body and said blades being of different material havingsubstantially the same coeflicient of expansion.

2. A balance system for magnetic balances comprising, in combination,anoscillatory balance body and magnetic blades operatively connectedthereto, said balance body being of iron and said blades of steel.

3. A balance system for magnetic balances comprising, in combination, anoscillatory balance body and magnetic blades operatively connectedthereto, said balance body and blades having substantially the samecoeflicient of expansion; and rods'extending from opposite ends of saidbalance body upon opposite sides of the balance axis of said balancesystem, one of said rods upon one side of the balance axis of saidbalance system being of zinc and another upon the opposite side of thebalance axis of said balance system being of invar, each of said rodscarrying a weight adjustable longitudinally thereof.

4. A balance system for magnetic balances comprising, in combination, anoscillatory balance body; magnetic blades carried thereby; and rodsextending from opposite ends of said balance body upon opposite sides ofthe balance axis of said balance system, said rods upon opposite sidesof the balance axis of said balance system having different coeflicientsof'expansion; and weights carried by said rods upon opposite sides ofsaid balance axis and adjustable toward and from the latter.

5. A balance system for magnetic balances comprising, in combination, ahollow oscillatory balance body and magnetic blades carried thereby,said balance body having broken away walls, to open the interior of saidbalance body to atmosphere.

6. A balance system for magnetic balances comprising, in combination anoscillatory balance body and magnetic blades, said magnetic bladesprovided with longitudinal slots and being secured to said balance bodyby screws extending through said slots and screwed into said balancebody, said balance body and blades being of material havingsubstantially the same coeilicient of expansion.

7. A balance system, comprising in combination, an oscillatory magnet;supporting means therefor; means, comprising a weight adjustablerelative to the axis of oscillation of said mag et, for adjusting saidmagnet in balanced position upon said supporting means; and meansoperatively connected to said magnet and responsive to variations intemperature to prevent deviation of said magnet from balanced positiondue to changes in temperature, said last named means possessing adifferent coeflicient of expansion upon opposite sides of the axis ofoscillation of said magnet; and a weight carried by said temperatureresponsive means and adjustable relatively to said axis of oscillation.

8. A balance system for magnetic balances comprising in combination anoscillatory balance body; supporting means therefor; magnetic bladescarried by said balance body; means for compensating temperaturechanges, said means being operatively connected to said balance body andresponsive to temperature changes and possessing a different coefficientof expansion upon opposite sides of the balance axis of said balancesystem; and means for adjusting said balance body in balanced positionupon said supporting means including weights carried by said temperaturecompensating means upon opposite sides of said balance axis, saidweights being relatively adjustable toward and from said balance axis.

9. A balance system for magnetic balances comprising, in combination, ahollow, oscillatory balance body and magnetic blades operativelyconnected thereto, the interior of said balance body being open toatmosphere.

10. A balance system for magnetic balances comprising, in combination, ahollow, oscillatory balance body and magnetic blades operativelyconnected thereto, said balance body and said blades being of differentmaterial having substantially the same coei'ilcient of expansion, theinterior of said balance body being open to atmosphere.

11. A balance system comprising, in combination, an oscillatory magnet;supporting means to support said magnet in balanced position; and meansat opposite sides of the axis of oscillation of said magnet andoperatively connected to the latter, said means being responsive tovariations in temperature and having a different coeflicient ofexpansion upon opposite sides of said axis.

12. A balance system comprising, in combination, an oscillatory magnet;supporting means therefor; means adiustably connecting said magnet tosaid supporting means nary adjustment of said magnet to balancedposition upon said supporting means; and means at opposite sides of theaxis of oscillation of said magnet and operatively connected to thesupporting means, said means being responsive to variations intemperature and having a different coeiiicient of expansion at oppositesides of said 8:13.

ERWIN ROUX.

to permit prellmi-

